# Understanding the math behind a falling object attached to a parachute

I'm trying to understand the mathematics behind calculating the total speed and force of a $40 kg_f$ object hooked up to a parachute, falling to Earth.

From what I understand, the formula for this is $$m \frac{dv}{dt} = (mass \times gravity) -Force_{deceleration}= 0$$

Here's where I'm confused: I understand that $m \frac{dv}{dt} = 0$ because once the parachute is deployed, the object reaches a constant speed at which it falls for the rest of the way down. However I also learned that $m \frac{dv}{dt} = F$, which is the total force of any moving mass. The object is falling to Earth and therefore it is moving, so how could the force, $F$, be equal to zero??

If you could help me get things straight, I'd really appreciate it. Thanks!

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My question asks, how could the force be $0$ if the object is falling? Obviously if it's falling, some force is acting on it. –  Imray Nov 8 '12 at 4:56